For Heaven’s Sake!

Rav Yisrael Salanter, zt”l, would warn his beloved students, “At the very least, don’t make yourselves out to be acting l’shem shomayim!”
He would explain, “A person who turns a blind spot to his natural ulterior motives and thinks he acts only for the sake of heaven is a terrible hazard to himself and others. If things do not go according to his plan, he naturally feels angry. After all, he is certain that his every movement is one hundred percent for the sake of heaven, so why isn’t Hashem allowing his altruistic plans to come to fruition? It is equally obvious to this person that anyone who is an impediment to his plans for whatever reason is in the wrong and may be crushed or pushed aside in any form he can get away with!”
Rav Yisrael would use this principle to explain the Mishnah in Avos in his uniquely pithy manner. “The sages taught, ‘Any conflict that is l’shem shomayim—סופה להתקיים—it is destined to exist in perpetuity.’—Talk about a thing that is sure to last forever!”
He explained this will a very direct parable. “Let’s say two competing shopkeepers are in a fight. Each one blames the other for stealing his customers. Even if they fight the whole year round, when erev Yom Kippur comes, they will surely regret their petty squabble and wish to make up. It is more than likely that one merchant will enter his friend’s shop and say something like, ‘Listen, Reb Chaim. Today is erev Yom Kippur. Let’s drink a l’chaim and forgive each other!’
“But if they fight ‘l’shem shomayim,’ will they make up erev Yom Kippur? Absolutely not! On the contrary, on erev Yom Kippur each will feel that he has the license to pursue his friend mercilessly. After all, each one already knows that he is completely l’shem shomayim. Keeping up the fight with his friend is nothing less than a mitzvah!”